Questions tagged [acid-base]

This tag should be applied to questions concerning acid and base reactions. An acid is capable of donating a hydron/ proton (Brønsted acid) or capable of forming a covalent bond with an electron pair (Lewis acid). A base on the other hand is a chemical species/ molecular entity having an available pair of electrons capable of forming a covalent bond with a hydron/ proton (Brønsted base) or with the vacant orbital of some other species (Lewis base).

Filter by
Sorted by
Tagged with
12
votes
4answers
23k views

Dissolving Organic Tissues [duplicate]

Watching some movie/TV this question came to mind, purely theoretical of course, if one wanted to dissolve a human corpse, like getting rid of a body after killing someone, is it better to use an acid ...
12
votes
2answers
3k views

Why are synthetic pH indicators used over natural indicators?

Synthetic indicators seem to be exclusively used when determining the pH of a substance with an indicator (with the exception of that school experiment where you boil cabbage to demonstrate natural pH ...
12
votes
3answers
7k views

Clear definition of a 'non-oxidizing acid'?

From the Beryllium article in Wikipedia: Beryllium dissolves readily in non-oxidizing acids, such as $\ce{HCl}$ and diluted $\ce{H2SO4}$, but not in nitric acid or water as this forms the oxide. I ...
12
votes
1answer
6k views

Is the equation pH + pOH = 14 valid at different temperatures?

$\mathrm{pH} + \mathrm{pOH} = 14$ For water at 60 degrees Celsius, $K_\mathrm{w} = 1 \times 10^{-13} = [\ce{H+}] \times [\ce{OH-}]$ Hence, $[\ce{H+}] = 1 \times 10^{-6.5} = [\ce{OH-}]$ So $\...
12
votes
2answers
2k views

How is volatility useful in the production of acids?

Sulfuric acid because of its low volatility can be used to manufacture more volatile acids from their corresponding salts. How does volatility affect the production of acids? Isn't it that sulfuric ...
12
votes
1answer
2k views

Why is boric acid soapy to touch?

Bases are soapy to touch because of soap formation on contact with lipids present on our skin. If this is the case then why and how is boric acid soapy to touch?
12
votes
3answers
18k views

Why are acetals stable to bases and nucleophiles?

Why are acetals stable to bases and nucleophiles? Could it be due to electronic effects? Lone pairs on the two oxygen atoms create an unfavorable environment for the approaching nucleophiles and ...
12
votes
1answer
2k views

Explanation of Lemon Juice-Invisible Ink

A cute homegrown spy-trick we all know: lemon juice invisible ink. But there is no scholary article available in the internet about this phenomenon. A rough explanation I found in Scientific American:...
12
votes
3answers
2k views

pKa differences and reactivity

I know a lot of chemists like to quote $\mathrm{p}K_\mathrm{a}$ values and subtract them to reinforce some notion about some acid-base reaction being highly favorable or highly unfavorable or whatnot. ...
12
votes
3answers
98k views

How do I calculate the degree of dissociation in equilibrium?

In my textbook, for calculating the percentage dissociation of $\ce{HF}$ for the given equation: $$\ce{HF + H2O <=> H3O+ + F-}$$ The solution is: Initial Concentrations $$[\ce{HF}] = 0.08~\...
12
votes
2answers
15k views

Do hydrogen halides (HX) form strong or weak acids?

I know that when dissolved in water, hydrogen halides ($\ce{H-X}$), become acids. I know that $\ce{HF}$ forms a weak acid, but can it be generalized that all $\ce{HX}$ acids do so?
12
votes
1answer
13k views

Basicity Alteration Due To Ortho Effect In Methoxy Aniline System

I wanted to ask something more in reference to this question Ortho-effect in substituted aromatic acids and bases Suppose instead of toluidine, 2-methoxyaniline and 3-methoxyaniline are present. Now ...
12
votes
1answer
8k views

Why would sulfuric acid turn gray/black?

About 2 years ago I purchased 2 liters of 98% concentrated sulfuric acid. It's in a standard poly bottle with leakproof lids, and originally was clear. Recently I noticed the acids have turned a dark ...
12
votes
1answer
1k views

How to analyze a acid and salt mixture using titrimetry?

Given a mixture of $\ce{HCl}$ and $\ce{MCl3}$ and the following dissociation constants for $\ce{M(OH)3}$, how can the concentrations of $\ce{HCl}$ and $\ce{MCl3}$ be determined separately by titrating ...
12
votes
1answer
8k views

Does unsubstituted benzoic acid not show resonance due to steric effects?

My book says that benzoic acid does not show resonance as the carboxylate anion and the benzene ring are not in the same plane due to steric effects. But there aren't any large groups in the ortho ...
12
votes
2answers
3k views

Why is trimethylsilanol a stronger acid than tert-butanol?

The Wikipedia article about trimethylsilanol says the following: Trimethylsilanol is a weak acid with a $\mathrm{p}K_\mathrm{a}$ value of 11. The acidity is comparable to that of orthosilicic acid, ...
12
votes
1answer
305 views

What is the structure of trifluoromethanesulfonic acid in the gas phase?

During an interesting discussion in our group’s seminar, the question arose what actually causes trifluoroacetic acid to be a much better nucleophile than trifluoromethanesulfonic acid. Part of the ...
12
votes
2answers
487 views

Why quaternary nitrogen but not tertiary oxygen?

Why do quaternary ammonium ions with a partially positive nitrogen form fairly readily and are often stable but tertiary oxygens, apparently called oxonium ions, are more rare/less stable? The trend ...
12
votes
1answer
436 views

Single electron reduction of ketone by Na or Zn

Whenever we add Na or Zn metal to a ketone, why does the electron prefer to attack the carbonyl bond and form a radical, instead of removing the acidic hydrogen and forming an enolate and $\ce{H2}$ ...
12
votes
1answer
7k views

Order of Acidic strength: Phosphorus oxoacids [duplicate]

I was asked to compare the acidic strength of the following phosphorus oxoacids, I thought the order (of strength) would be $\ce{H3PO4 > H3PO3 > H3PO2}$, because they have three, two and ...
12
votes
2answers
7k views

How to calculate partition coefficients?

Below is a transcript of this doubtful question: A weak monobasic organic acid $\ce{HA}$ is soluble in both water and $\ce{CHCl3}$. $\pu{500.0 cm3}$ of a solution of $\ce{HA}$ in $\ce{CHCl3}$, ...
11
votes
3answers
3k views

Is an acid a salt or not?

In our office, we discussed today what the exact definition of a salt is and whether an acid itself can be classified as a salt. Our first problem was that we couldn't get a definitive definition for ...
11
votes
4answers
69k views

Is sulfuric acid or hydrochloric acid stronger?

Of my belief, sulfuric acid might be a little stronger than hydrochloric acid. Because even though they both are strong acids, one mole of sulfuric acid produces two times as much $\ce{H+}$ as one ...
11
votes
1answer
19k views

Is an ester or a ketone more acidic?

Two organic chemistry textbooks I've read (by Bruice and by Tandon) say: Esters are more acidic than ketones, because the resonance between the two oxygen atoms gives less opportunity for the ...
11
votes
5answers
26k views

How to determine the pH of a mixture of two weak acids?

We have two solutions: Solution 1 is $\ce{HCOOH}$, its concentration is $c_1 = \pu{10^-2 mol/l}$, its volume is $V_1 = \pu{50 ml}$, and its $\mathrm{pH}_1 = 2.9$. Solution 2 is $\ce{CH3COOH}$, its ...
11
votes
4answers
56k views

Shouldn't the pH at the equivalence point always be 7?

I learned in class that the equivalence point in an acid-base titration is reached when the solution contains an equal amount of substance of $\ce{OH-}$ and $\ce{H+}$ ions. However, in a weak acid and ...
11
votes
1answer
1k views

Why are indicators used only in the form of dilute solutions?

Why are indicators used only in the form of dilute solutions? I get that indicators are a form of weak acids themselves, and the extent of their dissociation varies with the pH of the solution they ...
11
votes
1answer
14k views

Why does HNO3 not give off H2 when reacting with Cu?

A dilute solution of which acid is most likely to produce a reduction product other than $\ce{H_{2}}$ when it reacts with a metal? (A) $\ce{HF}$ (B) $\ce{HCl}$ (C) $\ce{HNO3} $ (D) $\ce{H2SO4}$ $\...
11
votes
2answers
5k views

More acidic - protonated carbonyl or protonated hydroxyl?

Consider two acetic acid derivatives, one with a protonated carbonyl oxygen and one with a protonated hydroxyl oxygen. An argument for the one with the protonated hydroxyl oxygen being more acidic ...
11
votes
1answer
7k views

Why is ammonia so much more basic than water?

The only reason I can think of is that the lone pairs in the oxygen in water are in lower energy orbital relative to the nitrogen in ammonia due to increased effective nuclear charge in oxygen. ...
11
votes
2answers
3k views

Acidity of hydrochloric acid in acetic acid

A question asked to find the $\mathrm pK_\mathrm a$ of $\ce{HCl}$ in acetic acid. The equation of $\ce{HCl}$ disassociating in water is: $$\ce{HCl + CH3COOH \leftrightharpoons CH3COOH2+ + Cl-}$$ I ...
11
votes
1answer
2k views

Why can't phosphorus trifluoride be used as a Lewis acid catalyst in electrophilic substitution of benzene?

Which of the following cannot be used as Lewis acid in the electrophilic substitution of benzene? $\ce{BF3}$ $\ce{SbCl3}$ $\ce{FeCl3}$ $\ce{PF3}$ My Attempt: $\ce{BF3}$ and $\ce{...
11
votes
1answer
3k views

exchanging H2O in buffer for D2O - pH vs pD?

I have TBS pH 7.4 buffer that I am exchanging all the water out for $\ce{D2O}$. How do I find out what the pD is after all the water is gone? I understand that pH meters don't work for deuterium, and ...
10
votes
2answers
5k views

How can I identify whether a substance is KOH or NaOH?

I've bought $\ce{NaOH}$ or $\ce{KOH}$ (I don't remember which one!) for my electrolyzer and I've tested it. Now I want to improve its performance and I was searching for a better electrolyte when I ...
10
votes
3answers
20k views

Is ammonium a strong or weak conjugate acid?

Ammonium, $\ce{NH_4^+}$, is the conjugate acid of ammonia, $\ce{NH_3}$. I have searched the Internet and so many different answers pop up. The rule of thumb that I read was that a strong acid has a ...
10
votes
3answers
826 views

Why can the lone pair not align with the phenyl moiety in 2,6-xylidine?

I am told that for 2,6-xylidine (2,6-dimethylaniline), the amino group cannot line up in such a way that its p-orbital is parallel with respect to the p-orbitals of the carbons in the ring. I've ...
10
votes
3answers
7k views

How can the equilibrium shift, while Kc remains constant?

Consider the following reversible reaction. $$\ce{Cr2O7^2-(aq) + H2O(l) <=> 2 CrO4^2-(aq) + 2 H+(aq)}$$ What will happen to the position of equilibrium and the value of $K_c$ when more $\ce{H+}$ ...
10
votes
2answers
3k views

Do acids really donate a proton?

Will acids really donate a proton? In an atom, the proton is inside the nucleus and I don't think a proton will go all the way out of atom dodging all electrons and enter into the nucleus of the base. ...
10
votes
2answers
8k views

Should bromine water be called a solution?

Bromine water is a reagent which is used to test for unsaturation in organic compound. It is $2.8~\%$ bromine in water. In many places, it is refer to as bromine solution. But it is observed that ...
10
votes
1answer
5k views

How do cloves break down plastic?

When my family buys powdered cloves in bulk, we put them in plastic until we get home - which takes at very most an hour. As soon as we get home, we transfer them into glass because we have had issues ...
10
votes
3answers
1k views

Where is the acid in DNA/RNA?

It is well known that the A in both DNA and RNA stands for acid, but where is the acid in chemical formula for the compound, and it is classified so based on what acid-base theory? Like Arrhenius, ...
10
votes
3answers
5k views

Acidity of o-halobenzoic acids

Rank the following compounds in decreasing order of acidity: 2-Fluorobenzoic acid 2-Chlorobenzoic acid 2-Bromobenzoic acid 2-Iodobenzoic acid My approach Since the ortho effect is proportional to ...
10
votes
2answers
17k views

Why is the iodide anion a good nucleophile but a poor base?

The $\mathrm{pK_{aH}}$ of $\ce I^-$ is very low which indicated that it is not favourable for it to bond with a proton. However, why would it be likely to bond with any other atom (mostly carbon when ...
10
votes
2answers
4k views

Is ciprofloxacin acidic or basic?

I would expect an aqueous solution of ciprofloxacin to be basic for the following reasons: The carboxyl group has pKa = 6.09 and the secondary amino group has pKa = 8.74. Because 8.74 is further from ...
10
votes
1answer
5k views

How does the HCl-KCl Buffer work?

I have just been studying the $\ce{HCl}$-$\ce{KCl}$ 'buffer', but there are still quite a few things I am uncertain about. I would appreciate any help in clearing up some questions I have. What I ...
10
votes
2answers
233 views

Why is d3-acetic acid more acidic than acetic acid?

The following table is from Solomons, Fryhle and Snyder Organic Chemistry, chapter 3, An Introduction to Organic Reactions and Their Mechanisms: Acids and Bases: Table 3.8 Isotopic substituents and ...
10
votes
2answers
6k views

Why does the ionic product of water remain constant after addition of non-neutral solute?

In my textbook, it is given that the ionic product of water $K_\mathrm{w}$ remains constant even when a non-neutral solute such as an acid is added to it. $$K_\mathrm{w} = \ce{[H3O+][OH-]}$$ When a ...
10
votes
4answers
4k views

Can water be a Lewis acid?

I asked this question to my teacher a few days ago. In a reaction such as $$\ce{NH3 + H2O -> NH4+ + OH-},$$ $\ce{NH3}$ is a Lewis base, but is $\ce{H2O}$ a Lewis acid? He said that it isn't. Now ...
10
votes
1answer
408 views

Esterfication of 2,2,2-triphenylethanoic acid

Explain the formation of (1,1,1-triphenylmethyl)methyl ether when a solution of 2,2,2-triphenylethanoic acid in concentrated sulfuric acid is poured in methanol. I cannot figure out where is one ...
10
votes
1answer
6k views

Why is picric acid more acidic than carbonic acid?

I just had a question in a test asking to compare the relative acidity of picric acid (TNP) and carbonic acid, $\ce{H2CO3}$ (not phenol). It turns out that TNP is more acidic. I have no idea why? Is ...

1 2
3
4 5
53